1. Field of the Invention
The present invention relates to non-porous, natural and synthetic polymeric articles having chemical and/or physical or other active properties or combinations of properties. The invention also relates to methods for preparing such articles.
More specifically, the invention relates to polymeric articles havng active properties and to the manufacture of such articles by applying to a surface of the article selected activating agents which are capable, in migrating or moving throughout the body of the article, of imparting an effective level of activity throughout the article and/or on a surface other than the one to which the activating agents have been applied.
2. Description of the Prior Art
It is known in the art that active properties can be imparted to polymeric articles by a variety of methods. One common method is to incorporate one or more activating agents into the polymeric compound during the mixing or blending phase prior to processing or manufacturing the article. Activation is accomplished by thoroughly distributing the activating agents throughout the compounding ingredients. For example, synthetic thermoplastics, natural and synthetic rubbers and other polymeric materials have been blended with activating agents such as, antibacterial, antistatic, electrically conductive and other chemically or physically active agents. The activated polymeric materials are then formed into sheets, fibers, rods or other configurations by molding, casting, extruding, calendering and/or other manufacturing or processing operations.
This method has many shortcomings. Often, certain active properties cannot be obtained, as when the presence of the activating agents in the polymeric compound causes difficulties during the processing, shaping and/or finishing of the article. In calendering, for example, the presence of the active ingredient often makes it difficult to attain an integral film. Activating agents which decompose or volatilize at the processing temperatures normally required for calendering cannot be incorporated in the pre-mix compound. Also, activating agents producing toxic vapors during processing require expensive manufacturing procedures, controls and equipment.
Another serious shortcoming of this method is that components, such as polymeric film used in laminates, must be produced with the activating agents incorporated in them prior to conversion to the finished article. When similar articles are made from active and inactive components, such as laminates made from active and inactive calendered polymeric film, the films must be kept in stock in both active and inactive grades. If various types of activity are desired, stocks must be maintained having each type of activity, which is an expensive procedure.
A second method widely used to impart certain active properties to the exposed or working surface is to apply a compound containing active agents to that surface. For example, anti-fouling marine paints, antifungal sprays and coatings, fire resistant coatings and antistatic coatings have been applied to the surface of the article. The activity of such coatings is superficially "skin deep" and surface activity is lost to the extent that the activated coating peels or is mechanically abraded, chipped or washed away from the inactive substrate. While this method affords certain flexibility in providing an activated surface, it is at best subject to limitations of available range of active ingredients that can be applied in this manner--plus limited service life and efficiency.
Another method for the production of activated articles is to expose the article to the vapors of a volatilized chemical. This ancient technique has long been applied to textiles, polymer sheets, or the like and comprises vaporizing a volatile agent, usually a biologically active agent, and then exposing the textile or other article to the vapors. A major disadvantage of this method, however, is that it requires special buildings, ventilation and recovery equipment, and safety procedures. Since the active agent has a volatilization temperature which necessarily is much lower than the melting point of the article to which the activating vapors are applied, the activation may be readily lost where the article is exposed to elevated temperatures. Thus, the treated material may be rapidly deactivated when subjected to wet or dry heat, for example, by exposure to steam sterilization or other high temperature washing procedure, intense sunlight, etc.
An important object of this invention, therefore, is to overcome the disadvantages of the prior art by providing a method for activating non-porous polymeric articles by applying the activating agents to one surface of the article so that the agents migrate throughout the body of the article and impart an effective level of activity throughout the article and on surfaces to which the activating agent has not been applied. The articles made by this method comprise an active layer which is applied on one surface of the article, and which contains an active migrating agent. The concentration of the agent is in excess of the concentration needed to provide an effective level of activity in the layer, and is sufficient, upon migration of the agent from the layer, to impart an effective level of activity throughout the entire article. The high concentration of the active migrating agent in the layer also provides a reservoir of activating material capable of replenishing the effective surface activity of the article.
The methods and products of this invention do not require extreme processing conditions so that volatile activating agents are conveniently used at normal temperatures; toxic agents can be handled safely; and a wide variety of inactive polymers can be given almost any desired activation. Only stocks of inactive articles are needed and the desired activation may be applied when desired. The activated article has long lasting properties which persist even if a surface layer is removed and which are replenished from the reservoir of activating agent contained within the active layer.
Disclosures of procedures representative of the prior art known to applicants are to be found in the U.S. Pat. Nos. 359,166, Mathieu, issued Mar. 8, 1887; 2,272,397, Becher, issued Feb. 10, 1942; 2,770,566, Ritter, issued Nov. 13, 1956; 2,785,106, Mendelsohn, issued Mar. 12, 1957; 2,919,200, Dubin et al, issued Dec. 29, 1959; 2,933,401, Schmitz-Hellebrecht, issued Apr. 19, 1960; 3,096,183, Geuth, issued July 2, 1963; 3,247,058, Hyman, issued Apr. 19, 1966; 3,279,986, Hyman, issued Oct. 18, 1966; 3,288,669, Heckenbleikner, issued Nov. 29, 1966; and 3,308,488, Schoonman, issued Mar. 14, 1967.